Generally, hydrogenation catalysts, such as hydrorefining catalyst, hydrotreating catalyst and hydrocracking catalyst comprise refractory oxides, such as alumina, silica-alumina, molecular sieve and the like, as the support, and one or more metals selected from the group consisting of molybdenum, tungsten, cobalt and nickel as the active metal components. Optionally, hydrogenation catalysts may contain auxiliary agent components, such as phosphorus, silicon, fluorine, titanium, zirconium, boron and so on. The metal components of the catalyst produced during the production process are usually present in an oxidation state. In the hydrogenation process, however, the active metal components of the catalyst have higher reaction properties when presenting in a sulfurization state (metals are present in the form of sulfides, such as Co9S8, MoS2, Ni3S2, WS2 and so on). The catalyst, thereby, needs to be presulfurized and converted to the sulfurization state thereof before being used. However, the presulfiding effects closely relate to the catalytic properties, and both the presulfiding process and the process control are essential.
In the prior art, there are merely two processes for presulfiding the hydrogenation catalyst, i.e. in situ presulfurization and ex situ presulfurization. In situ presulfurization is a process comprising feeding the catalyst into a reactor, and sulfiding by introducing a sulfiding agent, which is a common process. It has the disadvantage that the presulfurization lasts a long period of time, so as to have an adverse effect on the production efficiency. Ex situ presulfurization is a process in which the catalyst has been sulfurized or the sulfiding agent has been present before loading, and no introduction of a sulfiding agent occurs after loading the catalyst into the reactor. It has the advantage that the presulfurization lasts a short period of time, so as to improve the production efficiency.
Ex situ presulfurization concerns completely converting the metals on the catalyst to the sulfurization state thereof and then passivating; or adding a sulfiding agent before feeding the catalyst into the reactor, and then converting the active metals to the sulfurization state thereof in the reactor. Although it is easy to prepare, store, transport and feed by using said process, there are no sufficient interactions between the sulfiding agent and the catalyst metals, and the sulfiding agent easily loses and the concentrative thermal release readily occurs during the activation after the sulfiding agent-containing presulfiding catalyst is fed into the rector.
In the ex situ presulfurization of the hydrogenation catalyst, the sulfiding agent is generally selected from the group consisting of elemental sulfur, organic sulfides, inorganic sulfides, and mixtures thereof. Different addition methods and treatment methods will result in different presulfiding effects. Due to low cost and high utilization ratio, the elemental sulfur is used in many techniques as a sulfiding agent. When the elemental sulfur is used, it is usually introduced into the catalyst in the prior art by sublimation adsorption, melt impregnation, impregnation via dispersion in an organic solution, directly mixing with solid elemental sulfur powder, and the like.
U.S. Pat. No. 4,943,547 and U.S. Pat. No. 5,215,954 disclose adding elemental sulfur to an oil having a high boiling point or an organic solvent to produce a suspension beforehand, and then reacting with a fresh catalyst, or impregnating with an oil having a high boiling point or an organic solvent after the powdery elemental sulfur is contacted with the fresh catalyst. By said process, a certain sulfur-maintaining ratio may be achieved, but there is a problem of the concentrative heat release during the activation of the catalyst in the reactor. Moreover, the sulfur-maintaining ratio needs to be further improved. U.S. Pat. No. 6,077,803 describes dissolving the elemental sulfur and the organic sulfur in a solvent, and introducing elemental sulfur into the catalyst in the presence of a stabilizer selected from organic acids, thiols or organic alcohols, especially glycerine or hexose. But its disadvantage still lies in the problem of concentrative exothermic phenomenon.
In U.S. Pat. No. 5,786,293, U.S. Pat. No. 5,821,191 and EP352851, inorganic sulfides are as the sulfiding agent. The preparation process by dissolving the elemental sulfur in (NH3)2S solution is usually used therein. Complicated operation is the main insufficiency. Impregnation needs to be conducted at least twice so as to achieve some certain sulfur-loading amount, and the last drying must be carried out under an inert atmosphere.
In U.S. Pat. No. 5,017,535, EP 329499, U.S. Pat. No. 4,725,569 and EP130850, thiols, dimethyl sulfides, carbon bisulfide, and other organic sulfides containing 1-20 carbon atoms are used as the sulfiding agent. The elemental sulfur and organic sulfur are used together as the sulfiding agent in U.S. Pat. No. 5,922,638 and U.S. Pat. No. 5,397,756. The application of organic sulfiding agent has the main problem of higher amount and price. In addition, there is also some certain problem in transportation and loading process.
CN1107539C discloses contacting hydrocarbon compounds with the catalyst, and ex situ presulfiding with hydrogen and sulfur-containing compounds. Due to the presence of hydrogen and higher temperature (330° C. in the examples), the sulfides decompose to produce hydrogen sulfide (in fact, hydrogen sulfide is directly used in said patent). Hydrogen sulfide reacts with the metals on the catalyst to produce the metal sulfides, which is a process of complete presulfurization of the catalyst. However, the presulfurized catalyst easily combusts spontaneously, and there is safety problem in storage, transportation and loading. CN1400056A describes coating a sulfiding agent-containing presulfiding catalyst with an oxygen-containing organic compound containing at least 16 carbon atoms, treating at a temperature higher than 175° C. for a certain period of time, and then activating with hydrogen so as to reduce the self-heating of the catalyst. However, said process does not completely solve the self-heating problem of the catalyst in sulfurization state, and there is still a certain problem in storage, transportation and loading of the catalyst. CN1262305A discloses a process for presulfiding a hydrogenation catalyst, comprising mixing rubber sulfiding auxiliary agents, olefin-containing components, elemental sulfur and hydrogenation catalysts together, wherein rubber sulfiding auxiliary agents promote the combination of elemental sulfur with olefin-containing components and reduce the lose of sulfur. However, said patent does not solve the problem of concentrative heat release during the activation. U.S. Pat. No. 6,059,956 (CN1076635C) describes introducing elemental sulfur and organic polysulfides into the catalyst in the presence of olefin- or olefin fraction-containing components such as vegetable oil, then activating with hydrogen, and finally passivating with oxygen-containing gas. Said patent states that the passivation improves the activity of catalyst. However, since the metals on the catalyst are still in sulfurization state, said patent still has the aforesaid same problems.